This invention relates to a rotatable antenna feed polariser, and in particular to the means employed for rotating it.
In antenna systems, it is often required to include a polariser and it is sometimes necessary to change the direction of polarisation. For example, in a communication system, it may be necessary to select the direction of polarisation depending on the communication channel being used.
One known way by which this may be done is by means of a motor connected to the polariser via a speed reduction gearbox which is necessary to achieve sufficient accuracy of adjustment.
However, the amount and speed of rotation of the polariser cannot be controlled with complete accuracy because of stretching of the belt and backlash in the gearbox. Also, this known method can be expensive because of the cost of providing gears with minimal backlash.